Four-digit passcodes remain a weak point in iOS 8 data encryption

Longer passwords would be more resistant to brute-force attacks

The strength of Apple's revised encryption scheme in iOS 8 hinges on users choosing a strong passcode or password, which they rarely do, according to a Princeton University fellow.

Apple beefed up the encryption in its latest mobile operating system, protecting more sensitive data and employing more protections within hardware to make it harder to access. The new system has worried U.S. authorities, who fear it may make it more difficult to obtain data for law enforcement since Apple has no access to it.

Despite the new protections, data is still vulnerable in certain circumstances, wrote Joseph Bonneau, a fellow at the Center For Information Technology Policy at Princeton, who studies password security.

"Users with any simple passcode have no security against a serious attacker who's able to start guessing with the help of the device's cryptographic processor," he wrote.

If an iPhone is seized when it's turned off, it's unlikely that the keys can be derived from its cryptographic co-processor called the "Secure Enclave," which does the heavy lifting to enable encryption.

But if an attacker can boot the phone and get access to the Secure Enclave, it would be possible to start guessing passwords in a brute-force attack, and that's where the weakness lies.

Apple doesn't make it easy to completely copy all of the data on a device and boot it up using external firmware or another operating system, which would be an attacker's first step, Bonneau wrote.

His theory of how easy it would be to obtain the data from a device is dependent on an attacker being able to bypass the complicated "secure boot" sequence of an iOS 8 device.

"We'll assume this can be defeated by finding a security hole, stealing Apple's key to sign alternate code or coercing Apple into doing so," he wrote.

If that is possible, the attacker can begin guessing passcodes or passwords against the Secure Enclave. Apple's documentation suggests that such guesses could be conducted at a rate of either 12 guesses per second or 1 guess every five seconds.

By default, Apple asks users to set a "simple passcode," which is a four-digit numerical PIN, although users can set much longer pass phrases.

If an attacker can guess four-digit passcodes at 12 per second, the entire space of 10,000 possible PINs can be guessed in about 13 minutes, or 14 hours at the slower rate of one per five seconds, Bonneau wrote.

Apple could slow down the rate at which passwords can be entered, but that would probably annoy users. An alternative would be to limit the number of overall incorrect guesses and erase the phone's data, but that approach would require warning users that they're at risk of blanking their phone if they continue guessing, he wrote.

Even users who opt to set a longer passcode or phrase rather than a four-digit PIN are probably still at risk.

Bonneau said it's unlikely that users choose stronger passwords to protect their devices than Web services accounts, since "entering passwords on a touchscreen is painful."

The best advice is to create a password that is at least a 12-digit random number or a nine-character string of lower-case letters, he wrote. And do not use that password for any other services.

"These aren't trivial to memorize, but the vast majority of humans can do this with practice," Bonneau wrote.

If there's a fear a device may be seized, it's best to keep it off -- such as when crossing international borders -- as that offers the greatest level of encryption protection, he wrote.

Send news tips and comments to jeremy_kirk@idg.com. Follow me on Twitter: @jeremy_kirk

Join the newsletter!

Error: Please check your email address.
Rocket to Success - Your 10 Tips for Smarter ERP System Selection

Tags securitymobile securityAppleencryption

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Jeremy Kirk

IDG News Service
Show Comments

Cool Tech

SanDisk MicroSDXC™ for Nintendo® Switch™

Learn more >

Breitling Superocean Heritage Chronographe 44

Learn more >

Toys for Boys

Family Friendly

Panasonic 4K UHD Blu-Ray Player and Full HD Recorder with Netflix - UBT1GL-K

Learn more >

Stocking Stuffer

Razer DeathAdder Expert Ergonomic Gaming Mouse

Learn more >

Christmas Gift Guide

Click for more ›

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Edwina Hargreaves

WD My Cloud Home

I would recommend this device for families and small businesses who want one safe place to store all their important digital content and a way to easily share it with friends, family, business partners, or customers.

Walid Mikhael

Brother QL-820NWB Professional Label Printer

It’s easy to set up, it’s compact and quiet when printing and to top if off, the print quality is excellent. This is hands down the best printer I’ve used for printing labels.

Ben Ramsden

Sharp PN-40TC1 Huddle Board

Brainstorming, innovation, problem solving, and negotiation have all become much more productive and valuable if people can easily collaborate in real time with minimal friction.

Sarah Ieroianni

Brother QL-820NWB Professional Label Printer

The print quality also does not disappoint, it’s clear, bold, doesn’t smudge and the text is perfectly sized.

Ratchada Dunn

Sharp PN-40TC1 Huddle Board

The Huddle Board’s built in program; Sharp Touch Viewing software allows us to easily manipulate and edit our documents (jpegs and PDFs) all at the same time on the dashboard.

George Khoury

Sharp PN-40TC1 Huddle Board

The biggest perks for me would be that it comes with easy to use and comprehensive programs that make the collaboration process a whole lot more intuitive and organic

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?